Surface Science Studies of Nitrogen-Containing Cyclic Hydrocarbons on Platinum(111) and Tin/Platinum(111) Surface Alloys.

摘要

This thesis is based on two projects involving work on Pt(111) and Sn/Pt(111) surface alloys. The first project focused on the adsorption and surface chemistry of pyridine, cyclohexylamine, and piperidine, which were studied on a Pt(111) single crystal in ultrahigh vacuum (UHV) using temperature-programmed desorption (TPD). Piperidine was also studied on Sn/Pt(111) alloy surfaces. Some reversible adsorption was observed for each molecule, though the molecules mainly decomposed on the Pt(111) surface to form hydrogen, H2, hydrogen cyanide, HCN, and cyanogen, C2N2, as desorption products. Activation barriers for C-N bond cleavage are reported.;The second project was a study of the thermal decomposition of metal oxides formed by the oxidation of the (√3x√3)R30° Sn/Pt(111) surface with NO2, which was studied using high-resolution X-ray photoelectron spectroscopy (HR-XPS). The goal of the HR-XPS work was to determine if NO2 created an oxide of both Pt and Sn, and to clarify previous results from TPD studies on the oxidized Sn/Pt(111) surface alloys. Nitrogen dioxide, NO2, was not found to oxidize Pt; only Sn was oxidized. The Sn oxide underwent thermal decomposition at temperatures as low as 700 K. No oxygen was detected on the alloy surface above 743 K. NO2 was found to be a weaker oxidizing agent than ozone.